Version 1.4 - Universal Joint

The latest MOMDYN release is on the way, will be in the stores in the next day or so. The universal joint is the newest joint in the app, which creates a frame with rotations about two axes in an Euler sequence. You can see this in the graphic above, which consists of two universal joints, a rigid translation, and two rigid body boxes. Note the large angular displacements where you can observe the relatively slow oscillation about the vertical (Y) axis, and faster oscillation about the horizontal (X) axis. 

Besides the new joint, I did a whole lot of refactoring and bug fixing in this release. Added a whole lot of test coverage, so while this may not be the most feature-rich update, but I also hope it will be a lot smoother running and crash-free. I plan for this to be a trend; not too many new features going, but a lot of refinement to make the existing features work well. If there's anything you would like to see in upcoming versions, or anything that I'd royally screwed up, I would love to hear it!

 

Merry Christmas!

 Love, MOMDYN! And if you care for the sweet Christmas Music, check out the video of our Christmas tree on Youtube.

Its been a great couple of months for us, after officially releasing back in late September, we crossed the 1,000 download mark just a couple of weeks ago. We're planning a lot of cool stuff for the New Year, Just to name a few:

• Improved docs and built-in tutorial
• Change the colors of objects in the touch interface
• Legends in the plots, and ability to manipulate
• Document rendering
• Kinematic constraints

What are you hoping to see?

Version 1.2 - New 3-D Graphics

 

the latest update to MOMDYN should require little explanation, the diagram view has been updated to include a 3-D rendering. You can toggle between this new rendering and the previous 2-D drawing using the button labeled with either a [2] or [3] on the top line. In the 3-D view, tap and drag to translate the view, double-tap and drag to rotate.

The update is expected to be live in both the App Store and Google Play in a matter of hours. In the mean time, check out this video of the graphics in action.

For any Python and Kivy folks that are interested, these graphics are generated using a fork of the kivy3dgui library. There were only a few minor changes; I used a different glsl shader than the default because the initial one crashed on iPhone. Also a few minor syntax bugs that popped up, I suspect just a difference in Python version from what was used to create kivy3dgui versus what I'm using.

Other than that, the interface and simulation engine are all the same as before. 

New Tutorials

Along with the new release of MOMDYN onto the App Store and Play Store, I have created two new tutorials, for a simple pendulum, and a mass-spring-damper. These will be permanent pages (not blog posts), and I'm going to incorporate them and their corresponding Youtube videos directly into the app. Check out the videos below, and go download the app! (or join the beta, its free, just send me an email).

Version 1.0 ... Live in the App Store!

Guess what? As of today, the 16th of September, 2020, MOMDYN is available for the public on the iOS App Store! Check out that screenshot below, first (and only) result for multibody dynamics, how's that for fulfilling a life goal? 

I'm expecting to go live on the Play store in the next few days as well, then I'll have two buttons like a proper app. You'll see I'm charging $4.99, why? Because I can. The beta will stay free though, a willing tester will always be worth more to me than 5 bucks. If you're interested in joining the beta test, send me an email.

This is a culmination of almost a year of work for me, first while on sabbatical, and more recently in the early morning and late at night when I'm not working my regular job. I'm pretty excited to give it a run out in the wild west of mobile apps. Wish me luck!

What's new in version 0.10?

 Version 0.10 is up on Test Flight for iOS beta testers, and the Android version will be following shortly. This will be the *last* beta version before I release to the public on the App stores! This version contains all the basic features that I want for MOMDYN, and while I expect to keep on improving, I'm excited to finally release it into the wild. A little clip of the most recent version in action below. 

What you'll see in this latest version:

• Rigid Body Cylinder
• Rigid Body Cone
• Tabbed interface update

The cylinder and cone are very similar to the existing Rigid Body Box interface, replacing the two width and height arguments with a single radius argument. I had to do a bit of work to figure out how to make a nice wireframe graphic for these, which you can see some of at this Google Colaboratory notebook. A screenshot of that notebook is below, I used IPywidgets and the interact function to create the slider bars which rotate the cylinder and cone in the plot (note, you have to visit the link to use the interactions).

The new tabbed interface is purely aesthetic, I think putting them at the bottom better aligns with the visual qualities of a lot of modern iOS and Android apps. Also a few subtle changes to color themes, and made the report tabs all fit on a single line.

As I near release, I'll make note that I'm still looking for testers. I'll be doing this myself for the next couple of weeks, tapping my way through all the menus I can think of and seeing what breaks. Would like to have a few more folks to cover my blind spots. Besides that, I'm interested in what the users really want for future releases. I have my own ideas (more bodies and joints, 3-D diagram, ...), but the product really should be community driven. If you're interested, send me an email at mobilemultibodydynamics@gmail.com, and I'll add you to the list, its free, all I ask is you send me good useful feedback.

Spinning T-Handle

Just posted a new video to Youtube showing some of the new features in an upcoming MOMDYN update. Here I show combining a rigid cylinder and box to create a body similar to the T-handle from a famous video taken on the space station. Basically shows if you take a T shaped object and rotate it about its center axis, it is unstable. This is especially apparent in the zero gravity setting.

Video linked below. I'll have the beta app update in the next few days with the new cylinder and cone bodies, and some aesthetic updates (few last kinks to work out).